And that makes sense. By doing a job and not pursuing a career, the creator is able to devote more time and brain capacity towards making and promoting their comic. It allows them to focus on what's working and what isn't in their comic, and to improve their craft. But I'm struck by two considerations that a creator should keep in mind...
1) If the comic doesn't take off (and let's be honest -- most of them don't) then that job used to pay the bills becomes a career. And because the creator wasn't focusing on it as such, and because many of those jobs aren't very lucrative in the first place, that means their unintentionally adopted career has already plateaued. If they're doing at least a decent job, they'll probably get performance and/or cost of living raises from time to time, but their chances of significant advancement are limited. If you're not focused on trying to get a management job, they'll be more than happy to keep you slinging hamburgers or re-folding sweaters or whatever indefinitely.
Now some people can use this as an encouragement to put more effort into bettering their comic. "I don't want to be doing this shit job for the rest of my life, so I had better figure out how to kick ass as a comic creator." That works for some people but, of course, not everyone. If you want to take this approach, I suggest knowing in advance whether you're the type of person who's motivated that way or not.
2) The other consideration is that, if you're doing a job instead of pursuing a career, you're going to be viewed that way from the people who've hired you. We're increasingly living in a culture where employees of all sorts are just considered interchangeable cogs, but the farther down the pay scale you are, the more you're thought of in that way. Corporations and the people running them don't two shits about you, and will be more than happy to let you go if it means their year-end bonus is a little fatter. Which means that the income you'd be relying on while trying to get your comic career going is probably more tenuous than it should be.
This all then ties back to a point I tried to make a few years back. That if you're pursuing a career in comics, you need to have several irons in the fire financially. Even if your focus is entirely on your webcomic, you can't rely exclusively on advertising or Patreon or whatever. You almost need to constantly juggle several different revenue streams to help create a safety net. There's obviously going to be greater emphasis on some avenues over others, but it goes back to the old adage of not keeping all your eggs in one basket. You want to make sure you've got options open if/when something comes crashing down unexpectedly. Because your day job got cut, or your biggest sponsor closes up shop, or whatever.
The ongoing challenge is that you essentially never get much of a chance to rest. Because our economy is such that it's almost working against anyone not making six figures, it's going to be a near-constant uphill battle. I don't mean to come across as fatalistic or anything, I think assuming that your current status -- whatever it might be -- will be disrupted in the near future is what is going to be necessary to keep from not just staying in place but sliding backwards. If I'm overly cynical, that cynicism is directed at the society as a whole and not comics in particular.
Freelancing has always been a hard gig. It does allow a great deal of freedom that being a corporate drone does not. But it also comes with some additional challenges of keeping a constant vigil of your horizons, and ensuring that you're paying attention to where things are headed so that you can leap off sinking ships but still have some semblance of an escape plan laid out.